title: Embryo-transfer twinning and performance efficiency in beef production.
abstract: Effects of twinning on efficiency of beef production were estimated from results of bilateral transfer of two Angus x Hereford (AxH) embryos into each of 241 heifers and 84 cows (H, A, HxA or Holstein x H) over 4 yr. Calves were weaned at 180 d and fed either 220 d in a feedlot (1977) or 170 d on forage and 140 d in a feedlot (1978 to 1980). Effects of parity, twinning and sex of calf were estimated as covariates within year-breed of dam. Pregnancy at 45 to 60 d of gestation was 68% in heifers (H) and 74% in cows (C), with 40% single (S) and 60% twin (T) births. Dystocia was 28% in H vs 10% in C (P less than .05), and tended to be less (P greater than .05) for T than S in H. More placentas were retained (P less than .05) for T than for S in both H (35 vs 12%) and C (24 vs 4%). Twin gestations averaged 3 d shorter and subsequent calving intervals 13 d longer (P less than .05), but total calf mortality was slightly higher (P greater than .05). Abortions were 4% in H only. Twinning females lost maternal weight during late gestation (P less than .05) when crowding limited voluntary feed intake, while fetal requirements were 60% higher (P less than .01). Twins increased milk output 25% (P less than .05), but 11% higher feed intake maintained cow weight during lactation. Twinning reduced birth weight 13% and weaning weight 17% (P less than .05), but 400-d feedlot weight only 9% because of compensating feedlot gain. Twins gained 18% faster than S during postweaning 170-d forage feeding, but 5% slower in feedlot to 8% lighter 490-d weight (P less than .05). Assuming 40% higher veterinary and labor costs for twins, estimated integrated herd costs per unit of age-constant output value would be lower for T than for S production by about 24% for marketing either at weaning or at 400 d.
authors.affiliation: University of Nebraska, Lincoln 68583-0908.
authors.forename: P
authors.initials: P
authors.lastname: Guerra-Martinez
authors.forename: G E
authors.initials: GE
authors.lastname: Dickerson
authors.forename: G B
authors.initials: GB
authors.lastname: Anderson
authors.forename: R D
authors.initials: RD
authors.lastname: Green
mesh_terms: D000034:Abortion, Veterinary / Q000209:etiology; D000818:Animals; D001724:Birth Weight; D002417:Cattle / Q000254:growth & development / Q000502:physiology*; D002418:Cattle Diseases / Q000209:etiology; D003365:Costs and Cost Analysis; D004420:Dystocia / Q000209:etiology / Q000662:veterinary; D004435:Eating; D004624:Embryo Transfer / Q000662:veterinary*; D005260:Female; D007774:Lactation; D008297:Male; D010060:Ovulation; D010922:Placenta Diseases / Q000209:etiology / Q000662:veterinary; D011247:Pregnancy; D012098:Reproduction; D014427:Twins; D015430:Weight Gain